A technology of an oscillation circuit known as a ring oscillator having a configuration in which odd-numbered inverters are cascaded in a ring shape is known in the related art. An oscillation frequency of the ring oscillator is set by a delay time of each inverter. Thus, in a case where a ring oscillator with a low oscillation frequency is configured, the delay time is lengthened by, for example, increasing the size of a capacitor which is connected to an output terminal of each inverter. However, in a case where the size of the capacitor increases, power consumption increases when the capacitors are charged or discharged. In addition, the oscillation frequency varies depending on variation in manufacturing conditions or temperature change. Accordingly, it is preferable that an oscillation circuit is provided which can prevent the oscillation frequency from varying depending on variation in the manufacturing conditions or temperature change.